An explosion in northern Pakistan has killed at least 26, in an apparent sectarian attack staged by the Taliban.

The bomb was detonated in a busy market in a Shia neighborhood in the city of Parachinar. Scores of victims remain in a serious condition at the local hospital.

Accounts of the attack vary, with some claiming it was performed by a suicide bomber, while others blame a car containing explosives.

Fazal Saeed, leader of a splinter group of the Pakistani Taliban, has claimed responsibility.

“We have targeted the Shia community of Parachinar because they were involved in activities against us,” he told the Reuters news agency by telephone from an undisclosed location. “We also warn the political administration of Parachinar to stop siding with the Shia community in all our disputes.”

The Pakistan-Afghanistan border has been riven by sectarian fighting. The area is dominated by the Taliban and other al-Qaeda linked militant groups, who espouse Sunni Islam, and regard the sizeable Shia Islam minority in the region as traitors. The two sects exist as a result of a religious schism dating back 1400 years.

The Pakistani government has not been able to root out the Taliban militants, despite conducting frequent operations. It claimed to kill 11 of them only last month, but has only partial control of the unstable area.